You should be using iCloud for backing up your iPad. That is the seamless and easiest method to backup and restore when needed! If somehow you are not familiar with iCloud please refer to iCloud Setup Instructions
To learn how to backup to iCloud and set it so it's done automatically click How to back up your iPhone or iPad with iCloud - Apple Support
Finally, if you want to connect your iPad to the Mac to backup or offload some data then click How to back up your iPhone, iPad, and iPod touch with your Mac - Apple Support
Finally, if your iPad is working okay that is great however you may want to consider updating to a newer model. Simple to do and there are some really good deals out there right now. If you backup the old device to iCloud when you get a new iPad setting it up is a snap as it will restore your iCloud backup to the new device. I just bought a new iPad about 2 months ago, it took about an hour to restore my data and I was up and running. Also, you can get one with more storage than your old device and then. you won't have the issues you are currently running into!
